Inventories - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Inventory Disclosure [Abstract]
Inventory method			last-in, first-out (“LIFO”)
Effect of LIFO Inventory Liquidation on Income	$ 0.0	$ 0.0	$ 0.0	$ (0.9)
Replacement cost under stated LIFO value	34.2		34.2
Replacement cost of inventories, based on current market values					$ (17.7)
Lower of cost or market inventory adjustment	$ 32.1	$ 2.6	$ (34.2)	$ 41.5